1. Field of the Invention
The present invention relates to a stackable QFN semiconductor package and, in particular, to a super thin quad flat non-leaded semiconductor package without substrate.
2. Description of the Prior Art
A generally known U.S. Pat. No. 6,075,284 stackable semiconductor package can be stacked face to face, back to back by having its inner leads of the lead frame to extend protruding portions upward and downward respectively to form a package structure. But, with lead frame in such particular shape, it is difficult to process by method of etching or stamping. Besides, with inner lead of lead frame being located on two laterals of the package structure, it is categorized as dual-in-line package (DIP) and cannot be used to pack die(s) with more electrodes as a quad flat package (QFP) does.
According to shape of the outer lead, there are three types of Quad Flat Package (QFP), known as Quad Flat I-leaded (QFI) type, Quad Flat J-leaded (QFJ) type, and Quad Flat Non-leaded (QFN) type. With hidden lead and tightly sticking to circuit board during bonding, QFN package meets the demand of being light, thin, simple and compact for modem electricity components, especially components used in mobile electronics, such as cellular phone or notebook computer, etc.
A generally known Japan Patent No.10-74859 uses gold Circuits on the surface and edge of a substrate for electrical connecting to the die and integrate application of U.S. Pat. No. 6,020,629 DIP package to form a hollow as die container in the middle of the substrate. There are columns around the edge of the substrate for passing through top to bottom and construct a stackable package. But still it uses a complex substrate and is difficult to manufacture, the cost is higher and also the package structure is thick.
Therefore it is the first object of the invention to provide a stackable QFN semiconductor package, in which, by using inner lead of lead frame to form a thicker portion around the die and the thicker portion having its upper face and lower face exposed outside the molding compound, thus the QFN semiconductor package is able to be multiple stacked and also not to increase thickness of the package structure with simple structure.
It is the second object of the invention to provide a QFN package, in which, by using inner lead of lead frame to have its finger extend to the position above the die and to have the thickness of body of inner lead and thickness of the package structure being, of the same. Thus, the stackable QFN semiconductor package becomes a stackable QFN semiconductor package with a configuration of lead on chip or flip chip on lead frame.
In accordance with aspect of the invention, a QEN semiconductor package comprises a die having a plurality of bonding pads on its topside; a lead frame consisting of a plurality of inner leads around the die, wherein each inner lead being divided into the body and the finger extending from it; wherein, the body is thicker than the die and expose at least its upper face and lower face for outer electrical connection of the QFN package structure and the finger of the inner lead extend to above the die; an electrical connecting device for connecting bond pad of the die and finger of inner lead to electrically connect the die and inner lead of lead frame; and a molding compound that seals along edge of inner lead and at least seal said electrical connecting device and enhance the QFN semiconductor package stackable, thinner package thickness and simple structure.